Present regulatory conditions in the automotive market have led to an increasing demand to improve fuel economy and reduce emissions in present vehicles. These regulatory conditions must be balanced with the demands of a consumer for high performance and quick response in a vehicle. Variable displacement internal combustion engines (ICEs) provide for improved fuel economy and torque on demand by operating on the principal of cylinder deactivation. During operating conditions that require high output torque, every cylinder of a variable displacement ICE is supplied with fuel and air (also spark, in the case of a gasoline ICE) to provide torque for the ICE. During operating conditions at low speed, low load, and/or other inefficient conditions for a fully displaced ICE, cylinders may be deactivated to improve fuel economy for the variable displacement ICE and vehicle. For example, in the operation of a vehicle equipped with an eight-cylinder variable displacement ICE, fuel economy will be improved if the ICE is operated with only four cylinders during low torque operating conditions by reducing throttling losses. Throttling losses, also known as pumping losses, are the extra work that an ICE must perform to pull air around the restriction of a relatively closed throttle plate and pump air from the relatively low pressure of an intake manifold through the ICE and out to the atmosphere. The cylinders that are deactivated will not allow air flow through their intake and exhaust valves, reducing pumping losses by forcing the ICE to operate at a higher intake manifold pressure. Since the deactivated cylinders do not allow air to flow, additional losses are avoided by operating the deactivated cylinders as “air springs” due to the compression and decompression of the air in each deactivated cylinder.
In past variable displacement ICEs, when partially displaced, the operator would have to alter the position of an accelerator pedal to produce the same torque as when the ICE is fully displaced. Previous variable displacement ICEs were equipped with conventional pedal-throttle-wire couplings that required different accelerator pedal positions for the operation of a fully-displaced ICE and a partially-displaced ICE. The physical coupling between the accelerator pedal and throttle, and the inability to control throttle position as a function of displacement in previous variable displacement ICEs, prevented compensation in the accelerator pedal position for changes in output torque. The amount of air flow through the throttle required to generate the same torque for a fully-displaced and partially-displaced operation was different, requiring the physical position of the throttle plate and accelerator pedal to be different in the various operating configurations for a variable displacement ICE. Accordingly, the amount of movement in the accelerator pedal required to change the amount of torque for a fully-displaced and partially-displaced engine was also different. These differences in accelerator pedal operation, to generate the same torque for different modes of operation for a previous variable displacement engine, were nuisances to the operator of the vehicle.
The introduction of new engine control devices such as electronic throttle control (ETC), engine controllers, position sensors for pedal controls, and other electronics has enabled tighter control over more functions of an ICE. It is an object of the present invention to provide a variable displacement ICE whose operation is transparent to the operator of a vehicle.